–Do you know he will stay in America?Ten weeks.A. how often B. how long C. how soon D.

问题补充：

–Do you know he will stay in America? --Ten weeks.

A. how often

B. how long

C. how soon

D. how much

答案：

A. how often

(答案→)B. how long

C. how soon

D. how much

解析：回答语表示的时间的长度，用how long进行提问，故本题选B。